Thought chains are chains of thoughts that are vibrationally related to one another. Every thought you think creates a thought chain containing additional thoughts that are related to the first thought in the chain. Thus, if you think about something you want, you attract another thought that is related to it as you think that thought.
If you think about being wealthy for instance, you then attract another thought that is of a similar nature. If you think about a memory, you then attract another thought that is related to the memory being focused upon. This occurs with every thought you think too.
You can use thought chains to your advantage by creating desirable chains of thought. By thinking a thought that attracts desirable thoughts unto you, you can enhance the attraction process by thinking the most desirable thoughts possible to create the most desirable thought chains possible that will create the most desirable experiences possible.